The present invention relates generally to coating methods and systems and, more specifically, the present invention relates to a method and system for passing a substrate through a die that applies a coating on the surface of the substrate in a controlled manner.
Applying a coating substance to a substrate is well-known in the art. In applying a coating substance to elements such as wood, plastic, and metal, typically the coating substance is a paint that is applied with a solvent as a carrying agent. This allows the paint to coat the wood, plastic, or metal surface quickly and efficiently. Unfortunately, the solvent must evaporate out of the paint and the paint must dry before the surface can be handled.
An alternative method for applying a coating to a surface includes applying an electrostatic charge to the surface of the substrate, typically a metal, and then oppositely charging the paint so that as it is blown against the surface of the object, the opposite charges attract the paint to the surface. Once the paint powder attaches to the surface via the electrostatic charge, the object is heated in an oven to cure the paint for the final finish. This incurs the steps of cleaning the substrate surface in order for the paint to adhere to all portions of the surface, heating the substrate to a sufficient enough temperature to melt the paint for application, and finally cooling the substrate for handling.
A third method includes running the substrate via a conveyor through a ribbon of coating material to coat the exposed surfaces. The substrate is then inverted to coat the bottom surface as it passes through the curtain of coating material again or in a second stage. In this method, the coating material is a liquid, which typically requires the use of solvents to aid in the deposition of the coating material and the flow of the coating material during the coating step. Moreover, the coating material goes on wet and must dry prior to handling of the substrate or prior to application of any additional coatings that may be desired.
Solvent-based carriers and coating materials incur the added expense of the solvent required to carry the coating material. The drying stages typically require extra time, thus lowering through-put for assembly line finish work. Dry coating and heating of items to cure the paint coating also add to the finish time required, which further reduces throughput.
Accordingly, what is needed is a system and method for applying a coating to a substrate surface that eliminates the use of solvents, electrostatic adhesion, final heating stages, and the like. Further, what is needed is a method and system that provides a uniform and high level of finish on a substrate that allows the coating to dry in the shortest time possible, thus increasing throughput.